The present invention marks a specified vertical landmark on the face of a tooth crown and measures and marks its horizontal midpoint. These marks serve as the site to which an orthodontic brace is to be precisely located. U.S. Pat. Nos. 3,447,128 and 3,660,900 disclose a system whereby the orthodontist is directed to permanently mount brackets onto the individual teeth at a specified site on each tooth crown. Those patents do not disclose an instrument suitable for locating the proper position for the placement of an orthodontic bracket on a patient's tooth crown.
The broad faces of a tooth crown (not those that are the cutting surfaces) are referred to herein as the crown's "face." While these faces appear flat to the casual observer, they are in fact formed of humps separated by valleys, morphological landmarks resulting from the fusion of embryonic lobes during tooth formation. Molars typically have two such humps on each lateral face while all other teeth have three. Thus, the landmark for the face of a molar is in a valley, while that of other teeth is a hump. They both run vertically. To locate the bracket site, the orthodontist draws two lines, one representing the vertical landmark (the hump or groove) and the other the horizontal center of the vertical landmark. The bracket site is where these two lines cross.
In the past, locating the horizontal center line of the tooth crown required several steps. First, the orthodontist would measure the height of the crown from the gum line to the highest point of the tooth crown. This measurement would then be divided in half. Finally, the orthodontist would again measure the halfway distance from the highest point of the tooth crown to the center, marking the center with a pencil or other suitable marker. This method of finding tooth crown centers would be repeated for every crown scheduled for a bracket. These measurements required skill and dexterity on the part of the orthodontist. For each measurement, the patient's mouth would be oriented so that the orthodontist could manipulate the measuring tools. Repeated measurements required the patient's mouth to be sometimes uncomfortably manipulated to provide access to the tooth for the orthodontist.
The present invention provides a single tool by which the orthodontist can easily locate the horizontal center line of the tooth crown and mark it in a single operation. The invention eliminates the double measurement of each individual crown. The tool virtually eliminates any possibility of error by automatically centering a marker along the tooth. Thus, the level of skill and dexterity required by the orthodontist is greatly reduced. The time for installation and the discomfort to the patient are minimized by use of this invention.
Locating the vertical landmark of a front tooth is done by running a flat marking device down the crown's facial surface so that it will contact and mark only the outermost portion of the middle hump. Highlighting the vertical landmark of a molar is done by finding the center valley with the point of a marking element and running a pointed marker down the length of the valley. In a further embodiment of the present invention, both the horizontal and vertical center lines are marked with the same instrument, the hump with the flat side of the marker, the valley with the point.
The specific features and advantages of the invention can be better understood by reference to the accompanying drawings and the following detailed description.